Small Volumes Decompression #3 - Analysis of closed compartment in the Cabin Airline/PAX Configuration

Published: mar. 04 décembre 2018

The Airline/PAX Configuration

As shown in the Article #2, the Airline/PAX Configuration of the Numeric Corporate Jet considers an entire Main Cabin (Vol#1), Toilet (Vol#3) and Cockpit (Vol#100) in the Main Deck. The Cabinet to be analysed as the closed-compartment (Vol#2) is installed inside the Main Cabin (Vol#1).

Vol#01 is a large 5‘813ft³ volume.

Closed Compartment Vol#02 is simulated with several sizes: 5, 10, 15, 20, 25, 50, 75, 100, 125, 150 ft³. For each one of this volume, several gaps are simulated from 0in² to 70in².

Results for PAX configuration

[SPOILER ALERT!] For those who are in a hurry, here are the results obtained with ESonix V3 for the PAX configuration.

The Table below summarizes the results obtained by ESonix software after a run considering all parameters and data described here under.

As shown in this Table and previously explained, combinations between several Cabinet Volumes and Cabinet Vent were considered in the analysis. The pressure sustained for each combination is here presented in psi.

The table is formatted as in Boeing D655441 document, i.e. closed-compartment volume as horizontal entry and closed-compartment venting area as vertical entry. Differential pressures are rounded up to 2 digits.

For example, A 75ft³ closed-compartment with a 4in² gap would experience a 2.92 psi relative pressure!

As expected, the 0in² gap leads to maximum differential pressure whatever the Cabinet volume. Also, the greater the volume and the smaller the gap, the higher the differential pressure. For small volumes and big gaps (lower-left corner of the table),differential pressures are low enough to be rounded to 0.

NOTE: As the Numeric Corporate Jet has been designed for training purpose only, the results of this Table doesn’t correspond to any existing commercial aircraft. In a real case scenario, the generation of this Table is made possible with ESonix using TWEAKS parameters and BATCH mode analysis. Additional information about TWEAKS parameters and BATCH mode is available in the ESonix Manuals (see Manuals). Moreover, ESonix Tutorials provides a good opportunity to practice the use of those features (see Tutorials).

The Vent/Volume ratio curve

A convenient way to display this table is to show the differential pressure as a function of the vent/volume ratio (Airbus is using this representation).

But showing the vent/volume axis with a logarithmic scale is even more convenient:

The next step will be to calculate the same curves for the VIP configuration, where the aircraft volume in which the Cabinet is enclosed will be reduced from 5813ft³ to 653ft³. This is shown in Article #4.

Configuration Details

The following sections show how the volumes, their connections and the load case referring to this configuration are defined for the Esonix software.

Volumes

The table below reproduces the Esonix sheet Volumes.

      id    label           deck      sta     rbl       volume
[in]    [in]        [ft³]

1    Main Cabin        0     15500       0     10044550.4
2    Cabinet           0      7100     100     *variable*
3    Lavatory          0      6200     100       164764.8
20    Cargo E. Bay     -1      7000       0        1220480
21    FWD Cargo Bay    -1     11500       0         915360
22    Over Wing        -1     17000       0         274608
23    AFT Cargo Bay    -1     23000       0        1708672
24    Bulk Bay         -1     28500       0       225788.8
30    FWD Ceiling       2      7500       0        48819.2
31    Mid Ceiling 1     2     12500       0       140355.2
32    Mid Ceiling 2     2     21000       0       128150.4
33    AFT Ceiling       2     26500       0        97638.4
100    Cockpit           0      4000       0         488192


The Ceiling is divided in 4 volumes (Vol#30, Vol#31, Vol#32, Vol#33) which are connected to the Main Deck. The Cargo Deck is divided in 5 volumes (Vol#20, Vol#21, Vol#22, Vol#23, Vol#24) which are also connected to the Main Deck.

Cabinet Volume and its Connection

Although defined in the Esonix sheets Volume and Connections, the parameters (volume and vent area) of the Cabinet to be analysed as the closed-compartment (Vol#2), are modified by Esonix feature called Tweaks. Through this feature (Tweaks) the Cabinet Volume varied from 5 in³ to 150 in³ and the Cabinet Vent Area varied from 0 in² to 70 in².

NOTE: The user can check the Tutorial #6 of Esonix manual for additional information about the Tweaks feature of Esonix software.

The Airline/PAX Configuration analysis assumes an opening hole on the Main Cabin (Vol#01), where the Cabinet (Vol#02) is installed. The initial pressure differential between the cabin and the ambient is 8.6psi.

Connections

Four types of connection between aircraft volumes are considered in the Airline/PAX Configuration. They are:

Active Vents

The following figure illustrates the active vents (B01, B02, B03, B04, B05, B08, B09, B10, B11 and B12) considered in the Airline Configuration.

The following table shows how these active vents are considered by Esonix on its sheet Connections.

     id   vol_i  vol_j  comments                    vent_area    open._pres    cp      vent_area    open._pres   cp
i_to_j       i_to_j    i_to_j      j_to_i      j_to_i    j_to_i
[in²]         [psi]      [-]       [in²]        [psi]      [-]

51     1      31    Ceiling Blowout panel B01      0            0          0        387.50      0.217       0.6
52     1      31    Ceiling Blowout panel B02      0            0          0       1162.50      0.217       0.6
53     1      32    Ceiling Blowout panel B03      0            0          0       1162.50      0.217       0.6
54     1      32    Ceiling Blowout panel B04      0            0          0       1271.00      0.217       0.6
55     1      33    Ceiling Blowout panel B05      0            0          0       1271.00      0.217       0.6
58     1      23    Floor Blowout panel B08      310.00       0.435       0.6         0           0          0
59     1      23    Floor Blowout panel B09      310.00       0.435       0.6         0           0          0
60     1      24    Floor Blowout panel B10      310.00       0.435       0.6         0           0          0
61    20      21    Cargo Blowout panel B11      434.00       0.507       0.6       697.50      0.435       0.6
62    23      24    Cargo Blowout panel B12      465.00       0.435       0.6       620.00      0.507       0.6


Passive vents

The following figure illustrates the passive vents (V01, V02, V03, V04, V05, V06, V07, V08, V11, V12, V13, V14, V15, V16, V17, V18, V19, V20, V21), considered in the Airline Configuration.

The passive vent between Cabinet and Main Cabin is also defined here, although this connections is variable as explained below.

The following table shows how these passive vents are considered by Esonix on its sheet Connections.

    id    vol_i    vol_j    comments               vent_area      cp
i_to_j     i_to_j
[in²]       [-]

1      1        2     Cabinet to Main Cabin   *variable*    0.60
11      1       30     Passive Vent V01           15.5       0.45
12      1       30     Passive Vent V02           15.5       0.45
13      1       30     Passive Vent V03           15.5       0.45
14      1       30     Passive Vent V04           77.5       0.45
15      1       31     Passive Vent V05           15.5       0.45
16      1       31     Passive Vent V06           31.0       0.45
17      1       32     Passive Vent V07           46.5       0.45
18      1       33     Passive Vent V08           46.5       0.45
21      1       33     Passive Vent V11           46.5       0.45
22      1       33     Passive Vent V12           46.5       0.45
23      1       33     Passive Vent V13           77.5       0.45
24     30       31     Passive Vent V14           46.5       0.45
25     31       32     Passive Vent V15          108.5       0.45
26     32       33     Passive Vent V16           31.0       0.45
27     20      100     Passive Vent V17          542.5       0.45
28     20       21     Passive Vent V18          310.0       0.45
29     21       22     Passive Vent V19          310.0       0.45
30     22       23     Passive Vent V20          310.0       0.45
31     23       24     Passive Vent V21          232.5       0.45


Door Vents

The following figure illustrates the doors considered in Airline Configuration: Cockpit Door (D01) and Toilet Door (D02).

The following table shows how the doors and its vents are considered by Esonix on its sheet Connections.

The Cockpit Door (D01) is equipped with two blowout panels, see ids #2 and #3 in the table.

     id  vol_i  vol_j  comments                   door     vent_area    open._pres    cp      vent_area    open._pres   cp
i_to_j       i_to_j     i_to_j      j_to_i      j_to_i    j_to_i
[in²]     [in²]         [psi]       [-]       [in²]        [psi]      [-]

2    1    100     Cockpit door, Blowout 01      0      325.5        0.58         0.6         0           0          0
3    1    100     Cockpit door, Blowout 02      0      480.5        0.58         0.6         0           0          0
4    1      3     Lavatory swivel door D02   2480     2480.0        0.29         0.6      2480        0.29          0.6


Side Vents

The following table shows the Side Vents considered in the Esonix table Connections. Side Vents are passive vents between the Main Deck and the Cargo Deck.

    id   vol_i   vol_j   comments     vent_area       cp
i_to_j      i_to_j
[in²]        [-]

32     1      20     RHS Vent       37.2         0.45
33     1      20     RHS Vent       55.8         0.45
34     1      21     RHS Vent       10.1         0.45
35     1      21     RHS Vent       70.5         0.45
36     1      21     RHS Vent       23.3         0.45
37     1      22     RHS Vent      182.1         0.45
38     1      22     RHS Vent       40.7         0.45
39     1      23     RHS Vent      187.2         0.45
40     1      23     RHS Vent       49.6         0.45
41     1      24     RHS Vent        6.2         0.45
42     1      20     LHS Vent       77.5         0.45
43     1      20     LHS Vent       55.8         0.45
44     1      21     LHS Vent      119.4         0.45
45     1      21     LHS Vent       15.5         0.45
46     1      22     LHS Vent      182.1         0.45
47     1      22     LHS Vent       40.7         0.45
48     1      23     LHS Vent      187.2         0.45
49     1      23     LHS Vent       49.6         0.45
50     1      24     LHS Vent        6.2         0.45


NEXTSTEP…

The next Article will show the details and results of the Small Volume Decompression analysis considering the Numeric Corporate Jet in the VIP Configuration.

See here the list of Articles referring to the study of Small Volume Decompression:

• Article #1: Small Volumes Decompression #1 - Understanding the Problem

• Article #2: Small Volumes Decompression #2 - Airline/Pax, VIP configurations and Aircraft Parameters

• Article #3: Small Volumes Decompression #3 - Analysis of closed compartment in the Cabin Airline/PAX Configuration

• Article #4: Small Volumes Decompression #4 - Analysis of closed compartment in the Cabin VIP Configuration

• Article #5: Small Volumes Decompression #5 - Airline X VIP Results Comparison

• Article #6: Small Volumes Decompression #6 - Airline X VIP Results Comparison (Further Step)

• Article #7: Small Volumes Decompression #7 - Decompression Analysis considering the Cabinet Stiffness

• Article #8: Small Volumes Decompression #8 - Study summary and conclusions